12 INTRODUCTION. 



from these latter by decomposition. Correspondingly the oxidases 

 turn tincture of guaiac blue directly, while the peroxidases only have 

 this action in the presence of a peroxide.. The catalases do not give 

 any reaction with guaiac either directly or indirectly in the presence 

 of peroxides. 



According to the investigations of BACH and CHODAT 1 the condi- 

 tions are otherwise. According to the observations they have made 

 upon plants, there exist no oxidases, and what has been described under 

 this name is only a mixture of oxygenases and peroxidases. The 

 oxygenases are of a protein nature, contain manganese or iron, and 

 are converted into peroxides after taking up oxygen. These per- 

 oxides themselves have only a slight oxidizing power, but are made 

 active by the peroxidases. The peroxidases, which do not have the 

 slightest oxidizing power in the absence of peroxides, are not proteins. 

 In oxidation, according to the hypothesis of BACH and CHODAT, the molec- 

 ular oxygen is first converted by the oxygenase into peroxide. This 

 peroxide is activated by the peroxidase and then has strong oxidizing 

 power. The oxidizing power of the so-called direct oxidases is brought 

 about by a combined action of the oxygenases and peroxidases. 



The chemical nature of the oxidation enzymes is still unknown, 

 and the statements on this subject are very contradictory. Certain 

 oxidases are proteins, namely, nucleoproteins (SPITZER), others globu- 

 lins (ABELOUS and BIARNES), and still others, like the liver aldehydase 

 (JACOB Y) and laccase (BERTRAND), are of a non -protein nature. The 

 materials upon which the oxidation enzymes act may also be very dif- 

 ferent from each other. Thus the oxidases studied by ROHMANN and 

 SPITZER may by synthetical oxidation produce indophenol from a-naphthol 

 and p-phenylenediamine in the presence of alkali. The salicylase or 

 aldehydase detected in the liver and many other organs oxidizes many 

 aldehydes to their corresponding acids, but does not give the indophenol 

 reaction. The laccase isolated by BERTRAND from the juice of the lac- 

 tree has an oxidizing action upon polyhydric p-phenols, such as hydro- 

 quinone, but not upon tyrosine. The bodies called tyrosinases, first 

 found by BERTRAND 2 in certain fungi and later also found by BIEDER- 

 MANN, v. FURTH, and SCHNEIDER 3 in the animal kingdom, have, on the 

 contrary, an action upon tyrosine, converting it into colored com- 

 pounds. Another oxidase occurring in the liver and spleen, and called 

 xanthine-oxidase by BURIAN, has the property, as shown by SPITZER, 



1 Biochem. Centralbl., 1, pp. 417 and 457. 



2 In regard to the work of the various authors cited, see footnote 1, p. 11. 



3 Biedermann, Pfluger's Archiv, 72; v. Fiirth and Schneider, Hofmeister's Bei- 

 trage, 1. 



